There are two different Activities (QtActivity) contained inside an application - each one shown on a different display:

• the first activity is shown on a 1280x720 display - renders without any issues,
• the second activity - on a 4096x640 display - is not shown at all (black screen) until it is forced to redraw itself.

Additionally, each QML layout for both the activities has explicitly set size.

Swapping both the activities to display on the other corresponding screen does not resolve the issue - now the second Activity is shown on the first screen (properly scaled-down) and yet again the secondary screen is entirely black.

Workaround:

Currently, this issue can be resolved by calling QtActivityDelegate explicitly to set fullscreen mode somewhere at the beginning of the widescreen Activity's lifecycle:

QtNative.activityDelegate().setFullScreen(true);